A head-mounted display (HMD) device is a mobile, wearable, computer or video monitor that presents display imagery privately to its wearer. An HMD device may include an eyepiece for guiding a virtual display image into the wearer's field of view. Typically, the display image is formed on an emissive array, such as an organic light-emitting diode (OLED) array, or on a backlit, transmissive liquid-crystal display (LCD) array. In the current state of the art, transmissive LCD arrays exhibit significant radiant-energy losses, which may reduce battery life in an HMD device. OLED arrays are more efficient, but may not provide suitable output luminance, especially when the HMD device is used in an augmented-reality (AR) mode, where computer-generated virtual imagery is combined with real imagery from the outside world.